Vertically installed spar and construction methods

ABSTRACT

A vertically installed Spar-type floater for offshore wind turbine and related construction method are provided. The floating system is a gravity stabilized deep-draft floater including a plurality of vertically extending columns, each column containing a ballast material; a ballast tank coupled to the lower end of each of the columns; a top deck having a plurality of through-bores approximate its periphery coupled to the upper end of each of the columns; a wind turbine assembly supported by the top deck at the center; a plurality of mooring lines linking the floating system to the sea floor. The floating system has a temporary vertically towing configuration which: allows the entire, floating wind turbine system to be assembled at a quayside and towed vertically to an offshore site, and self-installed into operating configuration.

CROSS-REFERENCE TO RELATED APPLICATIONS

This present application claims the benefits of priority from the U.S.provisional application No. 61/310,473, entitled “VERTICALLY INSTALLEDSPAR FOR OFFSHORE WIND TURBINES AND CONSTRUCTION METHODS”, filed on Mar.4, 2010.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR

Not applicable.

REFERENCES

(1) U.S. Pat. No. 4,702,321, Filing date: Sep. 20, 1985, Issue date:Oct. 27, 1987

(2) U.S. Pat. No. 6,263,824, Filing date: Dec. 23, 1997. Issue date:Jul. 24, 2001

(3) Top Plants: Hywind Floating Wind Turbine, North Sea, Norway, PowerMagazine Article, Dec. 1, 2009

(4) U.S. Pat. No. 7,819,073, Filing date: Jun. 2, 2006, Issue date: Oct.26, 2010

(5) U.S. Pat. No. 7,612,462, Filing date: Apr. 24, 2008, Issue date:Nov. 3, 2009

FIELD OF INVENTION

Embodiments of present invention relate generally to the field offloating offshore wind turbines for offshore wind power generation. Moreparticularly, embodiments of present invention relate to a verticallyinstalled wind turbine Spar-type floater, which can be assembled at aquayside vertically and installed vertically together with the windturbine tower and rotor blades mounted in upright operating position,and towed at sea together with a wind turbine assembly mounted on thetop deck in upright operating position and installed vertically at anoffshore wind farm site

BACKGROUND OF INVENTION

Conventionally, a category of deep-draft caisson floaters, most commonlyreferred to as the Spar [Ref. 1 and 2], has been used for deepwater oiland gas drilling and production as shown in FIG. 1. A key characteristicof a Spar-type floater is that it usually has along slender body and isstabilized by gravity by maintaining its vertical center of gravitylower than the center of buoyancy. More recently the Spar floaterconcept has also been used as a floating wind turbine for offshore windpower generation [Ref. 3] as shown in FIG. 2. Such a conventionalSpar-type floater requires the buoyant hull be built onshore and towedoffshore in horizontal position and upended in deepwater for topsideinstallation. More particularly, a conventional Spar-type wind floateris built onshore and towed offshore in horizontal position as shown inFIG. 3, and upended in deepwater for installing the turbine tower androtor blades assembly by a floating heavy lift crane vessel as shown inFIG. 4. Such conventional Spar-type floater and offshore installationmethod is costly. A conventional

Spar-type wind floater could be vertically assembled at a quayside withwater depth in excess of 100 meter from the quay throughout to theoffshore wind farm site as mentioned in [Ref. 4]. However, there arevery few locations in the World, mostly in Norway, with such deep waterdepth for application. The present invention aims to provide aninnovative Spar-type floater with unique configuration which enables afloating wind turbine to be constructed, towed vertically and installedoffshore at significantly lower cost than a conventional Spar-typefloater.

SUMMARY OF INVENTION

A vertically installed Spar-type floating wind turbine system foroffshore Wind power generation and related construction methods areprovided. The present invention can be assembled at a quaysidevertically and towed at sea together with a wind turbine assemblymounted on the top deck in upright operating position and installedvertically at an offshore wind farm site to provide a morecost-effective floating wind turbine system for offshore wind powergeneration.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a prior art of a Spar-type floater used in oil andgas drilling production according to some embodiments of the presentinvention.

FIG. 2 illustrates a prior art of a Spar-type floater used in offshorewind power generation according to some embodiments of the presentinvention.

FIG. 3 illustrates a prior art of horizontal towing of a Spar-type windturbine floater according to some embodiments of the present invention.

FIG. 4 illustrates a prior art of installing a wind turbine tower androtor blades onto a Spar-type wind turbine floater by a heavy lift cranevessel according to some embodiments of the present invention.

FIG. 5 illustrates a perspective view of present invention of avertically installed Spar-type floating wind turbine system in permanentoperating configuration according to some embodiments of the presentinvention.

FIG. 6 illustrates a perspective view of present invention of avertically installed Spar-type floating wind turbine system in temporarytowing configuration according to some embodiments of the presentinvention.

FIG. 7 illustrates a front view of the vertically installed Spar-typefloating wind turbine system in permanent operating configurationaccording to some embodiments of the present invention.

FIG. 8 illustrates a side view of the vertically installed Spar-typefloating wind turbine system in temporary towing configuration accordingto some embodiments of the present invention.

FIG. 9 illustrates the quayside construction method and assemblysequence of the vertically installed Spar-type floating wind turbinesystem according to some embodiments of the present invention.

FIG. 10 illustrates the offshore installation method and sequence of thevertically installed Spar-type floating wind turbine system at anoffshore wind farm site according to some embodiments of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Preferred embodiments of the present invention are shown in FIG. 5through 10 above with detailed description as follows.

With reference to FIG. 5, a floating wind turbine system 2 in operatingconfiguration includes a plurality of vertically extending columns 4; aballast tank 6 coupled to the lower end of each of the columns 4; a topdeck 8 coupled to the upper end of each of the columns; a wind turbineassembly, comprising a tower 10, a nacelle 12 and rotor blades 14,supported by the top deck; and a plurality of mooring lines 16 linkingthe said floating system to the sea floor. The floating wind turbinesystem 2 has a referred range of in-service operating draft of 80 to 120meters. The columns 4 are empty and, the lower column segment contains aballast material most commonly sea water. With respect to the columns 4,the preferred number of columns is three and the preferred cross-sectionis circular which may be of same diameter throughout Or of differentdiameters at different elevations. The ballast tank 6 located at thebottom of the floater contains a ballast material most commonly of highdensity solid material, such as iron ore or sand or concrete, and isflooded in the operating configuration in the preferred embodiment. Thetop deck 8 is above the sea level supporting the turbine tower 10 whichhas the lower end coupled to a structural support located at the centerof the top deck 8. The ballast tank 6 and the top deck 8 can havevarious configurations which are, but not limited to, circular,triangular, rectangular, square, hexagon, octagon or star, or othernon-regular shapes. The preferred top deck 8 configuration has aplurality of through-bores at which the upper end of each of the columns4 is connected; Connections between the columns 4 and the top deck 8 canbe of welded or grouted by means of concrete. Connections between theturbine tower 10 and the top deck 8 can be of bolted, or welded orgrouted by means of concrete.

With reference to FIG. 6, a floating wind turbine system in temporarytowing configuration 18 includes a plurality of vertically extendingcolumns 4; a ballast tank 6 coupled to the lower end of each of thecolumns 4; a top deck 8 coupled to the upper end of the ballast tank 6;a wind turbine assembly, comprising a tower 10, a nacelle 12 and rotorblades 14, supported by the top deck 8; a plurality of stability tanks20, and a locking and quick release system 22 linking each of thestability tanks 20 to the top deck 8. The top deck 8 is preferred to beabove the sea level during the towing with offshore installationequipment mounted on the top surface. The stability tanks 20 providestability during the vertical towing of the entire wind turbineassembly. While FIG. 6 shows three stability tanks 20 each having a setof lock and quick release system 22, the present invention also coversvarious other stability tank and towing configurations such as but notlimited to a single stability tank configuration, two stability tankconfiguration, four stability tank configuration with correspondinglocking and quick release systems. The stability tanks 20 can bepurposely built or converted from existing marine cargo barges. Thelocking and quick release system 22 provides the connection between thetop deck 8 and the stability tank 20 during the towing and allows quickseparation during removal of the stability tank 20 after the floatingwind turbine completes the configuration change from the towingconfiguration 18 to the operating configuration 2.

FIG. 7 shows a front view of the floating wind turbine 2 in operatingconfiguration. FIG. 8 shows a side view of the floating wind turbine 18in towing configuration.

With reference to FIG. 9, the construction and assembly sequence at aquayside of the floating wind turbine system 18 in towing configurationis described. Step I shows the ballast tank 6 is first put on the waterand secured by temporary mooring to a quayside (not shown), and the topdeck 8 is put on top of the ballast tank 6. Step II shows the stabilitytanks 20 are connected to the top deck 8 and the columns 4 coupled tothe periphery through-bores and turbine tower 10 coupled to the centerof the top deck 8 supporting structure. In Step II, the columns 4 andthe turbine tower 10 can be lifted by a conventional crane on land andput on the top deck 8 one by one either in single piece or severalsegments. Temporary construction struts can be used to provide temporarystability for the extended columns 4. Step III shows the nacelle 12 androtor blades 14 are lifted by a conventional crane (not shown) andmounted on the turbine tower 10. In Step III, the nacelle 12 and rotorblades 14 can also be lifted separately one by one in a moreconventional way for wind turbine assembly. Step IV shows the floatingwind turbine system in towing configuration 18 is completely assembledat quayside. Sea-fastenings are provided to form a rigidly-connectedassembly. Solid ballast is put into the ballast tank 6. The floatingwind turbine system in towing configuration 18 is ready to be towedoffshore.

With reference to FIG. 10, the offshore towing and installation sequenceconverting the floating wind turbine system from the towingconfiguration 18 into the operating configuration 2 are described.Continuing from above Step IV Step V shows the floating wind, turbinesystem towing configuration 18 is towed vertically by a conventional tugboat (not shown) to the offshore wind farm site. Step VI shows thefloating wind turbine system towing configuration 18 is beingtransformed into the operating configuration 2 by lowering the columns 4vertically through the through-bores in the top deck 8. In this step,the stability tanks 20 are still connected to the top deck 8 to providestability for the entire assembly. The sea-fastenings for coupling thecolumns 4 to the top deck 8, and the ballast tank 6 to the top deck 8are removed. The ballast tank 6 coupled to the columns 4 moves downwardvertically under gravity to a deeper draft. Ballast water is pumped intothe columns 4 to further lower the ballast tank 6 to the final draft atwhich the upper end of the column 4 is just above the top deck 8 at apre-determined elevation for final connection. Permanent connections aremade between the top deck 8 and the columns 2. Step VII shows thestability tank 20 is being moved away from the top deck 8 by a tug boat(not shown). The locking and quick release system 22 is activated tocreate initial separation between the stability tank 20 and the top deck8 allowing the tug boat (not shown) to pull the stability tank 20 away.Step VIII shows lines are hooked up to the floating wind turbine system2 in operating configuration.

The above figures and description are preferred embodiments of thepresent invention and preferred main points of the construction methodsand assembly sequences for quayside assembly and offshore towing andinstallation. All modifications, equivalents, and alternatives to theabove preferred embodiments are to be covered in the character and scopeof the present invention.

1. A floating system comprising: a plurality of vertically extendingcolumns, each column containing a ballast material; a ballast tankcoupled to the lower end of each of the columns; a top deck having aplurality of through-bores approximate its periphery coupled to theupper end of each of the columns at the through-bores; a wind turbineassembly supported by the top deck at the center support structure; aplurality of mooring lines linking the floating system to the sea floor.2. The floating system according to claim 1 wherein said entire assemblycan be temporarily arranged in a vertically towing configuration,comprising: the vertically extending columns according to claim 1; theballast tank according to claim 1 coupled to the lower end of each ofthe columns; the top deck according to claim 1 coupled temporarily tothe upper end of the ballast tank, the top deck comprising a pluralityof through-bores approximate its periphery, a column extending througheach of the through-bores; the wind turbine assembly according to claim1 supported by the top deck; one stability tank or a plurality ofstability tanks coupled to the floating system; a locking and quickrelease system linking each said stability tank to the top deck to forma vertical towing assembly.
 3. The floating system according to claim 1wherein said deck comprising a structural system having a plurality ofthrough-bores approximate its periphery and a support structure for theturbine tower.
 4. The top deck according to claim 3 wherein saidthroughbore having a deck guiding system.
 5. The top deck according toclaim 3 wherein said deck guiding system having a locking and releasemechanism.
 6. The floating system according to claim 1 wherein saidcolumn having a column guiding system allowing said column to moverelative to the deck within the said deck throughbore.
 7. The deckguiding system according to claim 5 wherein said deck locking andrelease mechanism controlling the position of said column during saidfloating system offshore installation process.
 8. The floating systemaccording to claim 2 wherein said stability tank having a locking andrelease system linking the said stability tank to the said top deck. 9.The stability tank according to claim 8 wherein said locking and releasesystem having a quick release mechanism to allow quick separation of thesaid stability tank from the said deck during the said floating systemoffshore installation.
 10. The floating system according to claim 1wherein said ballast tank conventionally made of steel material havingthe option of being made of composite material with hybrid of steel,fiber and concrete.
 11. A method of vertically assembling the saidfloating system according to claim 2 at a quayside as illustrated inF1G. 9, comprising: Step I: coupling a deck to a ballast tank at aquayside, the deck comprising a plurality of through-bores approximateits periphery; Step II: coupling one or more temporary towing stabilitytanks to the deck; extending a column through each of the through-bores;coupling the lower end of each column to the ballast tank; Step III:coupling a wind turbine assembly to the top of the deck; Step IV:coupling a locking and quick release system and sea-fastenings to thedeck and each of the stability tanks, whereby the wind turbine, thedeck, the columns, the ballast tank, the stability tanks and the lockingand quick release system form an assembly, inputting a quantity ofballast material to the ballast tank;
 12. A method of vertically towingand installing a floating system according to claim 1 over a sea flooras illustrated in FIG. 10, comprising: Step V: continuing the steps fromclaim 11 above, towing vertically the assembly to an offshore wind farmsite; Step VI: removing the sea-fastenings between the deck and theballast tank, thus allowing the ballast tank coupled with the lower endof each of the columns to freely lower to a deeper draft, furtherallowing the upper end of each of the columns to reach a pre-determinedelevation approximate to the deck by inputting a ballast material mostlywater to the columns; coupling the upper end of each of the columns tothe deck by welding or grouting or bolting or other methods; Step VII:activating the quick release system and pulling away each of thestability tanks by using a tugboat, Step VIII: coupling the floatingsystem with the mooring lines to the sea floor.